I think those numbers are completely wrong but I'd happy hear how the poster calculated them.
Regarding MGX, I have spent 5 minutes looking at past presentation this morning and could have got many things wrong below.
However, there are three areas straight away; production, cash costs and reserves, which puts AGO in a totally different league to MGX.
1. Production
MGX has produced ~6mtpa for the last few years. This increase in FY13 to ~8mtpa for FY 13. However, this isn't indicative of the future production profile. TP is in its twilight year and will product 2.5mtpa for FY13 and then will be closed. Therefore production will be back to 6mtpa going forward.
Compare this to AGO who are already producing at 8 mtpa moving to 12 mtpa by the end of 2013. That is 50% higher annualised production rate (based on MGX's one off FY 13 rate) and a 100% higher based on MGX's normalised long run production rate of 6 mtpa.
Then, AGO have a pathway to 15 mtpa (2015) and 46 mtpa (2017) with 46 mtpa of port capacity . I can't see any similar upside for MGX.
2. Cash costs AGO's cash costs are around $46-50/t, MGX were $71/t for FY12. I don't think I need to say more.